An extremely large percentage of the world's vehicles run on gasoline using an internal combustion engine. The use of such vehicles, more specifically the use of vehicles which rely on fossil fuels, i.e., gasoline, creates two problems. First, due to the finite size and limited regional availability of such fuels, major price fluctuations and a generally upward pricing trend in the cost of gasoline are common, both of which can have a dramatic impact at the consumer level. Second, fossil fuel combustion is one of the primary sources of carbon dioxide, a greenhouse gas, and thus one of the leading contributors to global warming. Accordingly, considerable effort has been spent on finding alternative drive systems for use in both personal and commercial vehicles. Electric vehicles offer one of the most promising alternatives to vehicles that use internal combustion drive trains.
One of the principal issues involved in designing an efficient electric drive train and energy storage system is thermal management, primarily due to the required operating conditions of the battery cells and the ability to provide on-demand heating and cooling within the passenger cabin. To date, some electric vehicle thermal management systems have had limited capabilities, been overly complex, or both. For example, early generation electric vehicles often used multiple independent heat management subsystems. Such an approach required the use of numerous components (e.g., pumps, valves, refrigerant systems, etc.), and complex interacting controls.